1. Field of the Invention
The present invention relates to a precision machine vise that clamps two work pieces against oppositely facing surfaces of a fixed block in the center of a vise body and which has a double-threaded screw that simultaneously moves movable jaws toward oppositely-facing surfaces of the fixed block to clamp the work parts, and which includes a preload clutch that provides a preload force on one of the parts prior to final tightening.
2. Description of the Prior Art
Vises that use a center fixed block mounted on a body and movable jaws that move toward the fixed block for holding or clamping parts has been shown in various embodiments in the prior art. U.S. Pat. No. 62,584 shows a vise member that in its preferred embodiment has a center fixed jaw and two movable outer jaws that are forced in toward the center fixed jaw, utilizing either a cam actuator or a screw. The final clamping is made with equal pressure being exerted on the two parts by the cam member or by a screw.
Clamping devices which utilize screws having two threaded sections with opposite hand or lead threads and which actuate movable jaws against a center jaw are also shown in a number of ski clamping vises, such as U.S. Pat. No. 3,861,664. The vise in this patent includes a pair of jaws which float relative to a center jaw or reference member. The movable jaws are simultaneously actuated by a vise screw.
U.S. Pat. No. 2,299,294 shows a work holding device that provides for clamping a plurality of work pieces against members that can be fixed, or which can float for clamping.
U.S. Pat. No. 4,529,183 discloses a machine vise that has a center fixed jaw, and specific, sequential operation of movable jaws. The vise screw that operates the jaws has only one threaded section for one of the jaws. The one threaded section will first close one of the jaws until that jaw engages a work piece, and then the other jaws will be moved to clamp onto a second work piece in sequential operation and without requiring two threaded vise screw sections.